page_title: Polyyne
section_title: Organic and organosilicon polyynes
hierarchical_section_title: Polyyne / Synthesis / Organic and organosilicon polyynes
caption_attribution_description: English: Organic and organosilicon polyynes
context_page_description: In chemistry, a polyyne is any organic compound with alternating single and triple bonds; that is, a series of consecutive alkynes,
  ₙ with n greater than 1. The simplest example is diacetylene or butadiyne, H−C≡C−C≡C−H.
  These compounds have also been called oligoynes, or carbinoids after "carbyne"
  ∞, the hypothetical allotrope of carbon that would be the ultimate member of the series. The synthesis of this substance has been claimed several times since the 1960s, but those reports have been disputed. Indeed, the substances identified as short chains of "carbyne" in many early organic synthesis attempts would be called polyynes today.
  Polyynes are distinct from polyacetylenes, polymers formally obtained by polymerization of acetylenes. The backbones of polyacetylenes have alternating single and double bonds n. In biochemistry and plant biology, "polyacetylene" is routinely used to describe naturally occurring polyynes and related species.
  Along with cumulenes, polyynes are distinguished from other organic chains by their rigidity, which makes them promising for molecular nanotechnology. Polyynes have been detected in interstellar molecular clouds where hydrogen is scarce.
context_section_description: Using various techniques, polyynes H(−C≡C−)
  ₙH with n up to 4 or 5 were synthesized during the 1950s.  Around 1971, T. R. Johnson and D. R. M. Walton developed the use of end-caps of the form −SiR
  ₃, where R was usually an ethyl group, to protect the polyyne chain during the chain-doubling reaction using Hay's catalyst (a copper(I)–TMEDA complex).  With that technique they were able to obtain polyynes like Et
  ₃Si−(C≡C)
  ₙ−SiEt
  ₃ with n up to 8 in pure state, and with n up to 16 in solution.
  Later Tykwinski and co-workers were be able to obtain iPr
  ₃Si−(C≡C)
  ₙ−SiiPr
  ₃ polyynes with chain length up to C₂₀.
  A polyyne compound with 10 acetylenic units (20 atoms), with the ends capped by Fréchet-type aromatic polyether dendrimers, was isolated and characterized in 2002. Moreover, the synthesis of dicyanopolyynes with up to 8 acetylenic units was reported. The longest phenyl end-capped polyynes were reported by Cox and co-workers in 2007. As of 2010, the polyyne with the longest chain yet isolated had 22 acetylenic units (44 atoms), end-capped with tris(3,5-di-t-butylphenyl)methyl groups.
  Alkynes with the formula H(−C≡C−)
  ₙH and n from 2 to 6 can be detected in the decomposition products of partially oxidized copper(I) acetylide (Cu⁺
  )
  ₂C²⁻
  ₂ (an acetylene derivative known since 1856 or earlier) by hydrochloric acid. A "carbonaceous" residue left by the decomposition also has the spectral signature of (−C≡C−)
  ₙ chains.
caption: Organic and organosilicon polyynes
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